1. Field of the Invention
The present invention relates to an optical interrogation system that can interrogate a label-independent-detection (LID) biosensor and monitor a biological event on top of the biosensor without suffering from problematical parasitic reflections and/or problematical pixelation effects.
2. Description of Related Art
Today non-contact optical sensor technology is used in many areas of biological research to help perform increasingly sensitive and time-constrained assays. In these assays, an optical interrogation system is used to monitor changes in the refractive index or variations in the optical response/optical resonance of an optical biosensor as a biological substance is brought into a sensing region of the biosensor. The presence of the biological substance alters the optical resonance of the biosensor when it causes a bio-chemical interaction like material binding, adsorption etc . . . It is this alteration of the optical resonance that enables one to use the biosensor to directly monitor biological events in label-free assays where the expense and experimental perturbations of fluorescent dyes are completely avoided.
The optical interrogation system needs to implement some sort of resonance detection algorithm to determine whether or not a biological event (e.g., binding of a drug to a protein) occurred on the biosensor. To ensure that one can detect a small biochemical binding event, the resonance detection algorithm needs to be designed to sense small shifts in the resonance spectral location or the resonance angular location, wherein the shifts are often a very small fraction of the resonance width itself. For example, a typical resonance width for a resonant waveguide grating biosensor may be ˜1 nm, but a small biochemical binding event might present a change of only ˜0.001 nm. Unfortunately, today it is difficult to properly optimize the resonance detection algorithm because both the resolution and linearity of the optical resonance of a biosensor 102 may be adversely affected by: (1) the presence of measurement noise caused by problematical parasitic reflections; and/or (2) the presence of measurement artifacts caused by problematical pixelation effects. Thus, there is a need for an optical interrogation system that can optimize the detection of the optical resonance by addressing the problematical parasitic reflections and/or problematical pixelation effects. This need and other needs are satisfied by the optical interrogation system and method of the present invention.